U.S. Pat. Nos. 5,539,029 and 5,811,477 disclose aqueous asphalt emulsion compositions containing rubber particles and polymer latex in specific ratios and methods for preparing and using the rubber-containing asphalt emulsions. The methods of preparing the emulsions are advantageous over previous methods of mixing rubber particles with asphalt at temperatures above 300xc2x0 F., and typically between about 350xc2x0 F. and 500xc2x0 F. Such high temperature mixing is environmentally disadvantageous, especially when air pollution standards are violated.
Aqueous rubber-containing additive compositions may be used for improving asphalt compositions including recycled asphaltic concrete (RAP) and other asphalt paving and road surface compositions. The aqueous rubber-containing compositions of the present invention are fluid or semifluid additives comprising and preferably consisting essentially of a mixture of crumb rubber, aromatic petroleum hydrocarbon, surface active clay and/or rheological or thixotropic agent, and sufficient water to form the fluid or semifluid composition. The aromatic hydrocarbon and crumb rubber may be added to a mixture of water and clay and/or rheological agent, or the crumb rubber added to an aqueous emulsion of the aromatic hydrocarbon and a thixotropic agent. The additive is prepared at substantially ambient temperatures or temperatures below the boiling point of the liquid composition. The composition may also contain polymer latex. Other materials may be present in a final additive composition, as will be disclosed further hereinafter.